Haemophilus influenzae type b meningitis in children, Eritrea.

To the Editor: Bacterial meningitis is a major cause of death and disability in children worldwide: >1,000,000 cases and 200,000 deaths are estimated to occur each year. Neisseria meningitidis, Haemophilus influenzae type b (Hib), and Streptococcus pneumoniae are major causative agents of bacterial meningitis in children. A region in sub-Saharan Africa, extending from Ethiopia in the east to the Gambia in the west and containing 15 countries with >260 million people, is known as the "meningitis belt" because of its high prevalence of endemic disease with periodic epidemics caused by N. meningitidis.

Eritrea, a small country with an estimated population of 3.5 million in northeast Africa, is part of the meningitis belt. Eritrea gained independence in 1993 and borders the Red Sea on the east, Djibouti on the southeast, Ethiopia on the south, and Sudan on the north. Asmara, with a population of about 500,000, is the capital city. The estimated infant mortality rate is 73 deaths/1,000 live births.

In 2002, a prospective laboratory-based study was carried out in Asmara to gain insight regarding the distribution of bacterial agents causing bacterial meningitis in children. Starting in January 2002, cerebrospinal fluid (CSF) specimens were collected from every child who had a spinal tap administered at Mekane Hiwet Pediatric Hospital, Asmara. This facility selves as the national reference hospital for pediatric care. Within 1 hour of collection, all CSF specimens were processed at the Department of Microbiology, Central Health Laboratory. This laboratory, located <200 m from the Mekane Hiwet Pediatric Hospital, serves as the national reference health laboratory and is the only facility in Eritrea with the capabilities to perform cultures. Standard methods were used to process all specimens and to isolate and identify bacterial agents from the CSF specimens (1-3). All CSF specimens were cultured on chocolate agar plates with IsoVitalex supplement (BBL Microbiology Systems, Cockeysville, MD) and tested for bacterial antigens by using Wellcogen latex agglutination kits (Remel, Inc., Dartford, UK). Hib strain ATCC 49247 was used as the control strain. All Hib strains were tested for susceptibility to ampicillin, penicillin, chloramphenicol, gentamicin, and cefotaxime by using the disk diffusion method (BBL); isolates determined to be penicillin-resistant were also tested for [beta]-lactamase by using the Nitrocefin touch sticks (Oxoid, Basingstoke, UK).

From January 1 to December 31, 2002, a total of 81 CSF specimens were collected: 38 (47%) were from patients <1 year of age, 28 (35%) from patients 1 to 2 years of age, and 15 (18%) from patients 2 to 14 years of age. Twelve (15%) of the 81 specimens tested positive; 10 were positive by both culture and latex agglutination test (5 Hib, 2 S. pneumoniae, 1 N. meningitidis, and 2 Enterobacteriaceae), and 2 were positive only by the latex agglutination test (1 Hib and 1 N. meningitidis). The patients' age and sex and the results of microbiologic tests are presented in the Table.

This study preceded the implementation of the Integrated Disease Surveillance (IDS) in Eritrea (last quarter of 2002) and does not allow for calculation of incidence of Hib disease at the national level. However, implementation of IDS will enable microbiologists to prospectively monitor the incidence of infectious diseases, including meningitis caused by Hib.

In many countries, Hib is still reported as a major cause of bacterial meningitis (4-9), and while Hib meningitis has a relatively low case-fatality rate in developed countries (3% to 5%), high case-fatality rates (20% to 30%) are common in tropical Africa. Rapid laboratory diagnosis and treatment with appropriate antimicrobial drugs, such as third-generation cephalosporins, are crucial in reducing the risk for severe complications. The decrease in Hib meningitis cases after the introduction of Hib vaccination and the use of vaccine to control Hib meningitis are well documented (10-12). Additionally, the findings of this study suggest that Hib remains the leading cause of childhood meningitis in this region and lead us to advocate for the introduction of vaccination in Eritrea.

Table. Results of microbiologic tests of specimens from
five case-patients with Haemophilus influenzae type b (a)

                                         Antimicrobial
                                         susceptibility

Age/sex           Latex agglutination   Pen   Amp   Cefot
                         test

3 months/female        Positive          R     R     S
5 months/male          Positive          R     R     S
6 months/male          Positive          R     R     S
1 year/male            Positive          R     R     S
3 years/male           Positive          R     S     S

                 Antimicrobial
                 susceptibility

Age/sex           Chl   Genta   [beta]-lactamase

3 months/female    S      S         Positive
5 months/male      R      R         Positive
6 months/male      S      S         Positive
1 year/male        S      S         Positive
3 years/male       S      S         Positive

(a) Pen, penicillin; Amp, ampicillin; Cefot, cefotaxime;
Chl, chloramphenicol; Genta, gentamicin; S, sensitive; R,
resistant.

References

(1.) Popovic T, Ajello G, Facklam R. Laboratory manual for the diagnosis of meningitis caused by Neisseria meningitidis, Streptococcus pneumoniae and Haemophilus influeunzae. Document no. WHO/CDS/CSR/EDC/99.7. Geneva: World Health Organization; 1999.

(2.) Cheesbrough M. Medical laboratory manual for tropical countries, Vol II. London: Butterworth-Heinemann; 1985. p.160-74.

(3.) National Committee for Clinical Laboratory Standards. Performance standards for antimicrobial disk susceptibility testing. Approved standard, 7th ed. Document M2-A7. Wayne (PA): The Committee; 2000.

(4.) Uduman SA, Adeyemi E, El-Khadir A, Jose K, Benedict S, Boner A. Haemophilus influenzae type b still remains a leading cause of meningitis among unvaccinated children--a prospective CSF analysis study. J Trop Pediatr 2000;46:331-4.

(5.) Limcangco MR, Salole EG, Armour CL. Epidemiology of Haemophilus influenzae type b meningitis in Manila, Philippines, 1994 to 1996. Pediatr Infect Dis J 2000;19:7-11.

(6.) Lechmann D, Yeka W, Rongap T, Javati A, Saleu G, Clegg A, et al. Aetiology and clinical signs of bacterial meningitis in children admitted to Goroka Base Hospital, Papua New Guinea, 1989 1992. Ann Trop Paediatr 1999;19:21-32.

(7.) Sahai S, Mahadevan S, Srinivasan S, Kanungo R. Childhood bacterial meningitis in Pondicherry, South India, Indian J Pediatr 2001;68:839-41.

(8.) Migliani R, Clouzeau J, Decousser JW, Ravelomanana N, Rasamoelisoa J, Rabijaona H, et al. Non-tubercular bacterial meningitis in children in Antananarivo, Madagascar. Arch Pediatr 2002;9:892-7.

(9.) Matee MI, Matre R. Pathogenic isolates in meningitis patients in Dar Es Salaam, Tanzania. East Aft Med J 2001;78:458-60.

(10.) Dickinson FO, Perez AE, Galindo MA. Quintana I. Impact of vaccination against Haemophilus influenzae type b in Cuba. Rev Panam Salud Publica 2001;10:169-73.

(11.) Diaz JM, Catalan L, Urrutia MT, Prado V, Ledermann W, Mendoza C, et al. Trends of etiology of acute bacterial meningitis in Chilean children from 1989 to 1998. Impact of the anti-H, influenzae type b vaccine. Rev Med Chil 2001; 129:719-26.

(12.) Peltola H. Worldwide Haemophilus influenzae type b disease at the beginning of the 21st century: global analysis of the disease burden 25 years after the use of the polysaccharide vaccine and a decade after the advent of conjugates. Clin Microbiol Rev 2000;13:302-17.

Durgadas G, Naik * and Melles Seyoum *

* Central Health Laboratory, Asmara, Eritrea

Address for correspondence: Durgadas G. Naik, Central Health Laboratory, PO Box 1686, Asmara, Eritrea; fax: [phone]; email: [e-mail]